Keying system for electrical musical instruments



United States Patent [72] Inventor Walter Munch, Jr. 2,823,13 10 2/1958 Anderson 84/1.01

Covington, Kentucky 2,828,659 4/1958 Hanert 84/1.26 I [21'] Appl. No. 004,444 2,878,708 3/1959 Hanert 84/l.08 [22] Filed Jan. 25,1960 I 2,916,957 12/1959 Hanert 84/1.26 Continuation-in-part of Ser. No. 657,085, 2,951,412 9/ 1960 Hanert 84/ 1 .26 P d a y 6, abandoned- FOREIGN PATENTS [4 atente cc. 1, Assignee D. H. Baldwin p y 66,516 1/1927 Sweden 328/27 i i Ohio Primary Examiner-W. E. Ray a corporation f Ohio Attorney-Hurvitz & Rose [54] KEYING SYSTEM FOR ELECTRICAL MUSICAL INSTRUMENTS ABSTRACT: A gating C1l'CU1I for transmitting electric osc lla- 54C|aimS15DrawingFigs trons corresponding to musical tones compris ng a continuously operating source thereof, a load circuit, a common [52] (LS. Cl 84/l.26, return to which i source and said load circuit are both com 84/113? 328/84 216 nected, said gating circuit comprising a first gaseous discharge [51] Int. Cl GlOh l/02, tube and a second gaseous discharge tube connected in series 17/52 between said source and said load circuit, said tubes having ig- [50] Fleld oiSearch 315/845, Mon and extinction potentials Said source being coupled to 01. 205; 328/66, 67, 68, 69, 12 84, said first tube, said oscillations having a peak voltage insuffi- 210; i l'23(GDT)v L01, cient to ignite said tubes, said load circuit being coupled to the l-17 1'19 second of said tubes, and means for applying to said gating cir- [56] References Cited cuit at a point between said tubes a direct current potential of a value which will provide a potential above the ignition volt- UNITED STATES PATENTS age of said tubes, said source, said load circuit, and said means 2,484,612 10/1949 Dehn et al. 179/18 for applying said direct current potential being connected to 2,535,303 12/1950 Lewis 307/243 said common return, whereby said tubes are caused to fire al- 2,728,030 12/1955 Green 315/845 ternately depending upon the direction of the oscillations, and 2,81 1,069 10/ 1957 Faulkner 84/1.01 whereby a signal is produced in said load circuit in the form of 2,811,887 1 1/1957 Anderson et al. 84/l.0l direct current impulses of the same frequency as said oscilla- 2,8l9,640 l/1958 Anderson 84/1 .26 tions.

PATENTEU HEB] 1am I SHEET 2 OF 3 INVENTOR. 3/4 M J7 BY ATTORNEYS.

v PATENTEU DEE] I920 3 544 97 SHEET 3 OF 3 8/4 I /85 W m l I 846- I 86% 79 9 f a 7 INVENTOR.

141 41. TEE MuAlcl-l, J,.,

150.12. d/(WW ATTORNEYS.

KEYING SYSTEM FOR ELECTRICAL MUSICAL INSTRUMENTS This application is a contin'uation-in-part of my copending application Ser. No. 657,085, bearing the same title, filed May 6, 1957, which is abandoned.

The invention relates to keying or switching systems, particularly those including means for obtaining percussive effects in electrical musical instruments, by which is meant a circuit arrangement resulting in a decay of the tone produced by a generator in an output system upon release of a playing key, the decay being in accordance with a predetermined curve. Without such provision, the release of the key would result in an abrupt cessation of the tone.

The percussive system is applicable to key or switch operated instruments of monophonic and polyphonic character, and will be described herein in connection with an electric organ. It is one of the objects of this invention to provide a keying or gating circuit which will be devoid of key clicks even though a simple make-and-break switch is used. Other objects have primarily to do with the attainment of percussive effects.

In an electric organ, even when equipped with a percussive system, in sostenuto playing, the predetermined tone decay characteristics are not ordinarily apparent as such to the ear, although an effect of reverberation may be achieved. When, however, the instrument is played in a staccato fashion, the decay characteristics become immediately apparent. With proper control of timbre and of the duration and characteristics of decay, tones may be produced which simulate the tones of bells, bars, plucked strings (as in a harp), chimes, struck strings (as in a piano), and the like. With vibrato, the effects of instruments such as the vibraharp may be closely simulated. The percussive system is arranged to be made effective or ineffective as desired by means of suitable stop tabs. so that it can be used alone or as an adjunct to other organ voices.

Hitherto in the obtaining of percussive systems. it has been necessary to provide for each generator output to be given the percussive effects, a relatively elaborate gating circuit comprising an expensive thermionic tube and other components.

It is an object of this invention to provide a gating circuit having few components, and making use of simple and inexpensive neon bulbs as hereinafter set forth.

It is an object of the invention to provide percussive means which are simple in nature, readily adaptable to printed circuitry, and capable of being combined with the generating system of an electrical musical instrument so as to simplify construction and save space within the organ console.

it is an object of the invention to provide a percussive system which coacts with a high impedance switching means for the normal organ tones, whereby substantial savings are made in the construction of the organ.

The invention will be described in connection with an electronic instrument such as that set forth in U.S. Pat. No. 2,233,948, issued Mar. 4, 1941 in the name of Winston E. Kock as inventor. Reference is made to this patent for the details of exemplary generator systems (although others may be used as, for example, the generator system of U.S. Pat. No. 2,555,038 issued May 29, 1951 in the name of Edward M. Jones), means for simultaneously deriving octavely related oscillations in different headers and producing voices therefrom by utilizing the outputs of the several headers alone and in combination, means for obtaining voices rich in odd order harmonics by outphasing, means normally consisting of filter networks for controlling timbre, and for the general organization of an exemplary polyphonic instrument. It will be understood, however, that the utility of this invention is not confined to the specific instrument of the said Kock patent.

The objects of the invention set forth above, and others which will be set forth hereinafter or will be apparent to one skilled in the art upon reading this specification, are accomplished in that construction and arrangement of parts of which certain exemplary embodiments will now be described.

Reference is made to the accompanying drawings wherein:

FIG. 1 is a diagrammatic circuit representation illustrative merely of the principles of operation of a novel gating circuit of this invention.

FIGS. 20, 2b, 2c and 2d are respective representations of the wave forms of oscillations existing at various points in the circuit of FIG. 1.

FIG. 3 is a circuit diagram of a gating circuit containing means whereby the transmissivity of the circuit can be controlled at ill, and containing means for producing a controlled decay in the transmitted oscillations.

FIG. 4 is a circuit diagram of similar nature including means whereby the rate or time of decay can be varied.

FIG. 5 is a similar circuit diagram including means for controlling the shape of the decay curve.

FIG. 6 is a circuit diagram including means for minimizing high frequency feed-through.

FIG. 7 is a circuit diagram including all of the above features and showing how gating circuits for various oscillators may be combined in an output circuit.

FIG. 8 is a circuit diagram showing a modified circuit for achieving greater output.

FIG. 9 is a diagrammatic representation of a complete percussive system, including a partial showing of means for obtaining normal organ voices.

FIG. 10 is a circuit diagram of a type of gating circuit which is of especial value in applying percussion to the pedal clavier of an electrical musical instrument.

FIG. I] is a circuit diagram of a modification of the circuit of FIG. 10.

FIG. 12 is a diagrammatic representation of a pedal clavier switching system including the circuit arrangement of this invention.

The gating circuit of this invention makes use of inexpensive neon bulbs, by which is meant gaseous discharge devices preferably of a type in whicha pair of simple electrodes are mounted in parallelism in a neon atmosphere in a glass envelope. More expensive gaseous discharge devices may be emplayed; but the additional cost is not normally warranted. The preferred type of neon tube is the type known as NE-2. The bulbs are quite'small and are very low in cost. While this does not constitute a limitation on the invention, for the sake of clearness the invention will be described in connection with the use of neon bulbs having a firing potential of 70 volt and an extinction potential of 50 volts.

In FIG. I an oscillator or generator I is shown as connected to two neon bulbs 2 and 3 in series to an output point 4. The oscillator is indicated as grounded at 5. Between the two neon bulbs is shown a supply circuit containing a resistor 6 and a source of potential 7, there being at 8 a connection to a common return, conventionally illustrated as ground. Beyond the two neon bulbs there is another circuit containing a load resistor 9, and connected to the common return at 10.

The generator I may be thought of as producing oscillations having a peak-to-peak voltage of between 20 and volts with about equal positive and negative peaks. If the source of voltage 7 were not present, the illustrated circuit would not transmit oscillations from the generator 1 to the output point 4 because the peak signal amplitude of the generator is not great enough to fire the neon bulbs. If, however, the source of potential produces a potential of 70 volts or more, one of the neon bulbs will fire depending upon the direction of the generator voltage at the moment. As the generator voltage swings from positive to negative and back again, the neon bulbs will fire alternately. When the neon bulb 2 tires, the current flowing through the resistor 6 will flow through the generator. In this operation, the generator must supply a direct current path; but this is characteristic of the generators of the Kock patent referred to above in that the generator output is taken across a resistance to the common return, and similar provision may be made in the case of other generators. When the neon bulb 3 tires, the current flowing through resistor 6 will return to ground through resistor 9, developing at the output point 4 a rectangular halfwave, having, however,

. shows at 12 the wave form at the junction of the neon bulbs 2 and 3 and the resistor 6. When the voltage at this junction reaches the firing potential of the neon bulbs, the bulb 3 fires, lowering the potential at the junction to the operating potential of the bulb 3 plus the small voltage drop across the resistor 9. The neon bulb 2 is extinguished at this time since the volt-v age across it has become smaller than its operating potential. The bulb 3 will, however, continue to conduct until the generator voltage reaches 20 volts. At this time the firing potential of bulb 2 is reached. Bulb 2 fires and bulb 3 is extinguished. The voltage at output point 4 will be zero since the current in resistor 6 will be flowing through the generator. The bulb 2 remains conductive until the generator voltage reaches +20 volts, whereupon the bulb 3 tires, and the cycle is repeated. l

FIG. 20 will be seen to be illustrative at 13 of the voltage across the bulb 2; and FIG. 2d shows at 14 the voltage effective atthe output point 4. The current flowing in the resistors 6 and 9 depends upon the difference between the voltage applied by the potential source 7 and the operating potential of the bulb 3. It follows that the output voltage at the point 4 may be controlled by varying the voltage applied at 7.,Turning now to FIG. 3, where like parts have been given like index numerals, it will be noted that-a capacitor 15 has beeninserted between the resistor 6 and the common return at 8, and that the source of potential 7 has been eliminated as such. However, a source of potential, not shown but indicated by the legend +150V, has been connected to the point in the supply circuit between resistor 6 and capacitor 15 through a singlepole, single-throw switch 16.

Closing the switch 16 places 150 volts across the capacitor 15 and renders the system transmissive as hereinabove explained.

When the switch 16 is again opened, the capacitor 15 (previously charged while the switch was closed) will discharge through the resistor 6, maintaining the system in a transmissive condition until that voltage is reached at which the neon bulbs no longer fire. As the capacitor 15 which the neon bulbs no longer fire/As the capacitor 15 discharges, the output voltage at the point 4 will not remain uniform, but will decay, and the time of the'decay will be determined by the time constant of resistor 6 and capacitor 15 acting together. Thus a percussive effect as hereinabove defined is produced. Exemplary but nonlimiting values for elements 6, 9 and 15 have been indicated in FIG. 3.

In attaining various percussiveeffects, it is desirable to beable to change or vary the rate of time of the tone decay. In FIG. 4 where again like parts have been given like index numerals, there is shown a means whereby this may be accomplished. Another circuit is shown as connected to the supply circuit between resistor 6 and capacitor 15. This circuit contains in series a resistor 17, a neon bulb l8, and a single-pole, double-throw switch 19. One of the contacts of this switch is connected to the common return as at the other is connected to a source of positive potential, not shown, but marked +l00V as an exemplary value. a

If the switch 19 is in the common return position, the neon bulb 18 will fire when the switch 16 is closed. When the switch 16 is again opened, the current flowing in the neon bulb 18 will discharge the capacitor 15 more rapidly, thus shortening the decay time. When switch 19 is in the other position, the tube 18 will not fire, irrespective of the position of switch 16, and the decay rate will be unaffected, i.e. it will be the same as that obtained with the organization of FIG. 3.

In the simulation of certain percussive effects, a control of the shape of the decay curve is highly desirable. For example, in nianolike tones. the initial decay is very rapid, but this is followed by a period of relatively much slower decay. The system of this invention lends itself readily to the obtaining of eifccts of this character. FIG. 5 is illustrative of one mode of accomplishment. In this FIG., where again like parts are given the same index numerals. the neon bulb l8 isshown as having applied to it a positive potential of 75 volts. In the particular organization, this means that while the bulb 18 will flre when the switch 16 is closed, and will remain conductive for a brief interval after the switch 16 is opened again, thus increasing the rate of decay, it will continue to conduct for only a portion of the decay period. Thus, the tube 18 will reach its extinction potential prior to tubes 2 and 3, giving what may be termed a double-rate decay characteristic.

It will be understood by those skilled in the art that there is a small stray capacity across the neon bulbs. in some organizations, this may present no problem; but if difficulty is bad with feed-through (which feed-through increases with frequency), the circuit may be provided, as illustrated in FIG. 6, with a bypass to ground containing a small capacitor 21 from the point between the neon bulbs 2 and 3. Resistors 22 and 23, respectively ahead of and after the neon bulbs 2 and 3 in the output line of the oscillator, are added to prevent the circuit from going into relaxation oscillations when the bypass includ ing the capacitor 21 is used. It is readily possible to select a suitable small value for the capacitor 21, which will reduce the feed-through to an acceptable level without impairing the operation of the circuit. The component values shown in FIG. 7 indicate that the bypass impedance provided by the capacitor 21 (2O pluf.) is relatively low- (about 8M at 1,000 Hz.) compared to the nonconductive state of the gas tubes 2 and 3, but of the same order ofmagnitude when the gas tubes 2 and 3 are conductive. In other words, the bypass impedance of approximately 8M is comparable in magnitude to the 2.2M value of the gating sections which, in this FIG., comprise resistor 22 and tube 2 on the one hand and resistor 23 and tube 3 on the other.

FIG. 7 is illustrative of a useful gating circuit incorporating various of the features discussed above, and is also indicative of the way in which a plurality of thegating circuits may be coupled together. Like parts have been given like index numerals. The output point 4 of the illustrated gating circuit is shown as located on an output header 24 to which other gating circuits may be connected as the points 25, 26 and 27. The output to tone color filters may be taken at the point 28, main- 'tainedabove ground by a resistor 29. A dotted line box has been used in this FIG., to indicate that the switch 19, together with its connections to ground or the common return and to a source of positive potential of selected value, may be common to the several gating circuits, as at a collector 19a. The switch 16 for each gating stage will, of course, be a playing key operated switch, but it may be a simple make-and-break contact device. The switch 19 will normally be located on a panel of the instrument where the player will have access to it. Thus, it may be arranged to be operated by a stop tab, whereby the player can select the rate of decay desired. The percussive system will ordinarily have a plurality of tone color devices as hereinafter described, also actuated by stop tabs. It is within the scope of the invention to cause the stop tab selectors to actuate a switch or switches which select a rate of decay appropriate to particular tone colors, and/or to vary the shape of the decay curve as set forth above.

In FIG. 8, the circuit is essentially similar to those hereinabove described, excepting that the generator is isolated from the rest of the circuit by a capacitor 30, and a dc. path to the common return is provided through resistor 30a.

. Thus current is prevented from flowing back through the understood by the skilled worker in the art. The gating circuits take up little room and are preferably incorporated in the generator assembly of the instrument, especially since the generators may be connected directly to them, the switches such as switch 16 being located elsewhere, i.e. in connection with the playing keys. I

Furthermore, the gating circuits disclosed are high impedance circuits and work very well in an electrical musical instrument with high impedance switching means for the usual organ tones such, for example, as capacitative switching means. Thus, in a complex polyphonic instrument, where the playing keys each operate a plurality of electrostatic switching means (so as to derive oscillations of different footages in different headers), it becomes possible to connect the several generators directly with the appropriate electrostatic elements of the appropriate switches, and to the gating circuits of this invention without the use of the isolating resistors heretofore found necessary with low impedance output paths. The cost of these resistors is thus saved. Because electrostatic switches produce a gradual onset of the tones, there is no need to employ gradual contact switches of the resistive type.

In the percussive voices themselves, a gradual onset of the tones is not necessary, but is produced to a considerable degree by the fact that the capacitor must charge through resistor 31 when the switch 16 is closed, and the attack may be controlled by varying the value of resistor 31. The structures of this invention are thus adapted to be used as keying or switching means for the tones of electrical musical instruments, with or without percussion; to avoid key clicks, in lieu of other keying devices such as resistive switches or the capacitative keying switches just mentioned.

While other forms of tone color circuits such as ordinary filters may be employed, it is preferred to use vacuum tube filter or voicing circuits with percussive circuits, particularly in view of the output wave form illustrated in FIG. 2d hereof. The percussive gating circuits of this invention are capable of use in the manner set forth in the copending application of Alfred J. Bissonette and Frank J. Kramer, Jr., Ser. No. 62l,769, filed Nov. 13, I956 and entitled ELECTRONIC MUSICAL IN- STRUMENT, now US. Pat. No. 2,986,964. A simplified arrangement of this type is illustrated in FIG. 9. The so-called vacuum tube filters are preferably vacuum tube amplification stages employing negative feed back; and the voicing obtained is a function of the frequency selectivity of the passive elements in the feed back loop. Each stage is characterized by a parallel T" network. In a three-voice system, three types of networks may be employed, viz. '(a) a network tuned to exhibit a null in the fundamental frequency of operation; (b) a network tuned to exhibit a null at twice the fundamental frequency; and (c) a network tuned to exhibit a null at four times the fundamental frequency. Since the networks are used in a negative feed back loop, the overall stage frequency will peak at the null frequency. Thus, if the null is at the fundamental frequency, the output will be nearly sinusoidal. If the null is at twice or four times the fundamental frequency, entirely different and rich wave forms will result. It will be understood that many more than three voices may be provided if desired. Bissonette and Kramer found that the vacuum tube filters would each handle the output of four generators related as adjacent semitones. This, coupled with'the fact that a filter with a negative feed back loop tuned to null at twice the fundamental frequency of a given oscillator constitutes a filter with a negative feedback loop tuned to null at the fundamental frequency of an oscillator an octave above the first, and so on, enabled Bissonette and Kramer greatly to diminish the number of vacuum tube filter circuits required for any given organ range. This system is equally applicable to the gating circuits of the present invention.

The gaseous tube percussion circuits of this invention are particularly adaptable, without the need for additional impedance-matching circuitry, to systems employing high-impedance key switches such, for example, as disclosed by Hugh LeCaine in an article entitled Touch-Sensitive Organ Based on an Electrostatic Coupling Device," in Journal of the Acoustical Society of America Vol. 27, No. 4, 78l-786, July 1955. To keep signal-to-noise ratios at acceptable values, such switching systems necessitate relatively high generator voltages, of the order of that required to operate percussion circuits of the type disclosed in my application herein. In FIG. 9 the generator 1 is shown as coupled directly to the percussive or gating circuit 32, which may be the circuit illustrated in FIGS. 7 or 8 hereof. Three other adjacent generators marked 1a, lb, and 1c are shown as directly coupled respectively to their percussive circuits 33, 34, and 35. The generators I to It will encompass a range of four semitones, e.g. if generator I is C, generator Ia will be C5, generator 1b, D, and generator lc, D The gating circuits respectively for these several generators will be coupled together as at 24 so that their outputs can be transmitted selectively to various vacuum tube filters as hereinafter explained.

Each gating circuit will have its switch 16, 16a, etc. connected as shown to a bus fed by dc source 16d. In FIG. 9 the generator 1 is shown as having a branch connection 36 to a header 37, preferably through a high impedance switch diagrammatically indicated at 38 as a variable capacitor. Any form of switch may be employed. Such a switch may be but is not limited to that described in the LeCaine article referred to above. It will be key actuated, as will the switch 16. A key has been diagrammatically shown at 39, and dotted lines indicate that this key simultaneously actuates capacitive switch 38 and the make-break switch 16 of the gating circuit 32. Similarly the generator 1a will have a branch lead 40 to the header 37, the lead containing a capacitive switch 41, and so on for the other generators.

It will be understood, particularly in the light of the Kock patent above referred to, that each of the generators may also have branch connections to capacitative switches operated by octavely related keys, the switches being connected to various headers in which the tones may be correlated in terms of footage. This has not been illustrated. Yet again, in a plural keyboard instrument, the generators may have branch connections to switches operated by the keys of the other keyboards. This also has not been shown.

The rectangles 42, 42a, and 'so forth in FIG. 9 indicate other groups of four adjacent oscillators together with their respec tive gating stages. These oscillators will also be connected to the header 37 through groups of capacitative key switches such as are diagrammatically illustrated at 43, 430, etc. At intervals along the header 37 capacitors 44, 44a, etc. may be inserted for the purpose of attenuating groups of notes in lower registers with respect to higher registers, thus producing a more uniform loudness in view of the opposite effect of lowpass filters which will be employed for tone color.

The header 37 is connected to an amplifier indicated at 45. This amplifier may, if desired, be a cathode-follower amplifier circuit such as is shown in FIGS. 6-13 on page 106 of Electron-Tube Circuits, by Seely (McGraw-Hill, 1950).

The output of the amplifier 45 is provided with a plurality of paths to a reproduction system through various tone color filters as taught in the Kock patent above set forth. The rectangles 46, 47, 48 and 49 are representative of tone color filters. The filters are provided with switches 50, 51, 52 and 53 normally operated by stop tabs on the console of the instrument. There may be as many tone color filters as desired for tonal flexibility in the instrument and various ones of the tone color filters may derive oscillations from other headers than the header 37 or from combinations of headers containing octavely related oscillations, or from combinations of headers in which respectively the oscillations are out of phase, all as taught in the Kock patent.

The output from the tone color system may be delivered by a lead 54 to a preamplifier 55, and thence to a main amplifier with volume control and to one or more loud speakers (not illustrated).

The output from the gating stages 32 to 35, collected in the header 24, may be delivered through a switch 56 and lead 57 to a vacuum tube filter of the type described above and diagrammatically illustrated by the rectangle 58. Or the output may be delivered through a switch 59 and a lead 60 to a vacuum tube filter 61. Yet again, the output may be delivered through a switch 62 and lead 63 to a vacuum tube filter 64. It may be assumed for purposes of this disclosure that the filter 58 peaks at the average fundamental frequency of the oscillations coming through the gating stages 32 to 35, that filter 61 peaks at twice that frequency, and filter 64 at four times that frequency. v

Switches 56, 59 and 62 are parts of relay gang switches, as illustrated. The gang switches are provided with electromagnetic operating devices actuated by stop tab switches controlling the percussivewaves. These have not been illustrated but will be readily understood by the skilled worker in the art, or can be ascertained from the copending Bissonette and Kramer application referred to above.

In a similar fashion, and by means of the same tone color relays, the group of gating stages represented by the rectangle '42 can be connected selectively to vacuum tube filters 65, 66

and 67. The group of gating stages represented by the rectangle 42a is similarly connectable to vacuum tube filters 68, 69 and 70. The average frequency of the oscillations in the gating stages forming the group 42b is octavely related to the average frequency of the oscillations in gating stages 32 to 35. As a consequence, switch 71 will connect the output of 42b to vacuum tube filter 61, now acting as a filter peaking at the fundamental frequency. Similarly, switch 72 will connectthe output of 42b to vacuum tube filter 64 now acting as a filter peaking at twice the fundamental frequency. Switch 73 will connect the output of 42b to vacuum tube filter 74. Thisarrangement is repeated throughout the-assembly.

Whilethree vacuum tube filters have been shown for each group of gating stages, their number may be multiplied as desired for different tonal effects. It is also within the scope of the invention to employ band pass filters of linear character for the obtaining of some orall of the percussive voices.

The output leads of the various filters in the percussive assembly are connected to abus 75 which carries the oscillations to the preamplifier 55.

In the arrangement illustrated, the instrument may be played with organ voices alone, or with percussive voices alone, or with a combination of the two types of voices. Where organ voices are combined with percussive voices, the effect of percussion will still beapparent in staccato playing, but the tonality will be modified, thus providing great richness and variability of tone. It will also be apparent that percussive effects may be used as accents in the playing of organ music.

The gating circuits of this invention have the advantage of being comparatively inexpensive so that without unduly increasing the cost of the instrument percussive effects may be made available on more of the claviers of the instrument or in a greater range on any one clavier, or both. Especially valuable results are obtained by making percussive effects available on the pedal clavier.

A basic circuit comprising a resistor, 'a first gaseous discharge tube, a second'gaseous discharge tube and a second resistor in cascade, as shown in FIG. 7, for example, requires a generator source which is substantially devoid of a dc. component. Where the oscillationsource delivers such a component, an rc network between the generator and the gating stage may be employed as shown in FIG. 8. It was found that the blocking capacitor could be placed between the first and second gaseous discharge tubes if the generator signal contained a dc. component having a value no greater than about to 30 volts, and providing the gaseous discharge tube was of the NE-2 type. Such a circuit is illustrated in FIG. 10 where following the oscillation generator I there is a resistor 22, a neon tube 2, a capacitor 76, a neon tube 3, a resistor 23 and a load resistor 9 in cascade. Resistors 77 and 78 are connected respectively to either side of the capacitor 76 and to the key switch'l6 and one side of a second capacitor 15. The other side of the last-mentioned capacitor is grounded or connected to the common return; and a source of d.c. potential 79 is connected between the switch 1 6 and the common return.

This circuit has the additional advantage that the firing potentials of the neon tubes do not have to be as well'matched as in other circuits hereinabove described.

A further simplification of this circuit is indicated in FIG. 11 where like parts have been given like index numerals. Here a single resistor 80 located between the neon tubes takes the place of the two resistors 22 and 23 and serves the same pur poses. It suppresses the high frequency oscillations which occur when no series resistance is used. I

FIG. 12 illustrates a pedal percussive system using the gating circuits of FIG. 11. Sources of oscillations are indicated respectively at C, Off, D,C. For the derivation of oscillations of nonpercussive character from these generators, seriesconnected switches are employed, each connected with a key of the pedal clavier. The first of these switches is designated at 81 and is a single-pole, single-throw switch. Others of these switches, designated 81a, 81b, 81n are double-throw, singlepole switches. The connection of these switches in series insures that only one note in the pedal clavier can sound at any onetime; and it is only necessary to connect the lead from the last of these switches through appropriate tone color circuits (not shown) to a pedal output system 82. r

The gating circuit of FIG. 11 will be recognized in the dotted box 83. Other boxes 83a, 83b, 83n will be understood as representing similar gating circuits. Each gating circuit has a single-pole, single-throw switch 84, 84a, 84b, 8421. These switches are connected together and through the source 79 of d.c. potential tothe common return.

The several gating circuits are connected to a common bus 85 which will normally contain a percussion stop switch 86. The bus may be connected to a separate pedal percussion output system 87, or if desired, the output system 87 may be omitted and output of switch 86 may be connected to the pedal output System82. The switches 84 etc. of the gating stages are mechanically coupled with the generator switches 81 etc. of the pedal keyboard as indicated by dotted lines. The system is a simple one especially desirable for pedal percussive use where the low frequencies involved minimize feedthrough. 1

Iclaim:

l. A gating circuit for transmitting electric oscillations corresponding to musical tones comprising a continuously operating source thereof, a load circuit, a common return to which said source and said load circuit are both connected, said gating circuit comprising a first gaseous discharge tube and a second gaseous discharge tube connected in series between said source and said load circuit, said tubes having ignition and extinction potentials, said source being coupled to said first tube, said oscillations having a peak voltage insufficient to ignite said tubes, said load circuit coupled to the second of said tubes, and means for applying to said gating cir cuit at a point between said tubes adirect current potential of a value which will provide a potential above the ignition voltage of said tubes, said source, said load circuit, and said means for applying said direct current potential being connected to said common return, whereby said tubes are caused to tire alternately depending upon the direction of the oscillations, and whereby a signal is produced in said load circuit in the form of direct current impulses of the same frequency as said oscillations.

2. The structure claimed in claim 1 wherein said means for applying said direct current voltage comprises a circuit containing in series a resistor and capacitor, and connected to said common return, with a connection including a switch between a source of direct current voltage and a point on said circuit between said resistor and said capacitor, whereby said gating circuit becomes operative when said switch is closed and upon the charging of said capacitor by said source. and whereby upon the opening of said switch said gating circuit remains in operation for a brief time during partial discharge of said capacitor, producing a percussive effect in said output signal.

3. The structure claimed in claim 2 wherein to the same point as said switch there is connected in series a resistor, a third gaseous discharge tube and a single-pole double-throw switch, one contact'of which is connected to the common return and another contact of which is connected to a source of direct current voltage, whereby variations in the decay rate may be obtained.

4. The structure claimed in claim 2 wherein to the same point as said switch there is connected in series a resistor, a third gaseous discharge tube, and a source of direct current voltage, the source of direct current voltage being of such value that the said third gaseous discharge tube, upon the opening of said switch, remains conductive for a shorter interval than the effective time of discharge of said capacitor, whereby a percussive effect is obtained characterized by decay at successively different rates.

5. A percussive-type gating .circuit for employing a directcurrent voltage to connect an audio signal source to an output system, comprising in cascade between said source and said output system a firstresistor, a first gaseous discharge tube, a first capacitor, a second gaseous discharge tube, and a second resistor, in combination with third and fourth resistors respectively connected from either side of said first capacitor to one side of a second capacitor and to a'single-pole, single-throw switch having a connection'to a source of said direct-current voltage, said second capacitor having a connection to a common return path for said signal source and said direct-current voltage source.

6. A gating circuit for employing a direct-current voltage to connect an audio signal source to an output system, comprising in cascade between said source and said output system, a first gaseous discharge tube, a first capacitor, a first resistor, and a second gaseous discharge tube, in combination with a third resistor having one end connected from the first tube and first capacitor junction to one side of a second capacitor and to one side of a single-pole, single-throw switch, and a fourth resistor connected from the" second tube and first resistor junction to said one side of said second capacitor and to said one side of said switch, said switch being connected at its other side to asource of said direct-current voltage, the other side of said second capacitor being connected to a common return path for said signal source and said direct-current voltage source.

7. In a tone gating system for an electronic organ, a continuously operating tone generator, a tone bus for collecting said tone, a load connected to said bus, a diode gating circuit connected in series between said tone generator and said tone bus, said diode gating circuit comprising at least one diode, means for at will rendering said gating circuit conductive, said means comprising a source of direct current voltage, a switch connected in a series circuit extending between said source and and an electrode of said at least one diode, and means consisting of a relatively large bilateral resistance connected in said series circuit and having a value greater than the conductive impedance of said at least one diode but smaller than the nonconductive impedance of said at least one diode, said direct current voltage having a value sufficient to gate on said gating circuit, wherein said tone generator, said at least one diode and said load form a series circuit loop, said load including tone color filters and an electroacoustic transducer.

8. The combination according to claim 7 wherein is further provided a storage capacitor connected across said source of direct current voltage and said switch, and having a value selected to sustain the conductive gating condition of said gating circuit for an audibly sensible sustain time interval on opening of said switch.

9. The combination according to claim 8 wherein is further provided a circuit in shunt to said storage capacitor, said circuit including a further diode and a further resistance in series with each other, said further resistance having a value selected to bleed said storage capacitor at a rate selected to sensibly decrease said sustain time interval while said diode is conductive.

10. The combination according to claim 9 wherein is further provided means comprising a voltage source selected to vary the conductivity of said further'diode at will, said last means including switch means for at will selectively enabling and disabling said voltage source.

11. In a tone gating system for an electronic organ, a continuously operating tone generator, a tone bus for collecting said tone, a load connected to said bus, a diode gating circuit connected in series between said tone generator and said tone bus, said diode gating circuit comprising a first diode and a second diode in series with each other, means for at will rendering said gating circuit conductive, said means comprising a source of direct current voltage, a switch connected in a series circuit extending between said source and an electrode of one of said diodes, and means consisting of relatively large bilateral resistance connected in said series circuit and having a value greater than the conductive impedance of either of said diodes but smaller'than the nonconductive impedance of either of said diodes, said direct current voltage having a value sufficient to gate on said gating circuit, wherein said tone generator, said diodes and said load form a series circuit loop, said load including tone color filters and an electroacoustic transducer.

12. The combination according to claim 11 wherein is further provided a storage capacitor connected across said source of direct current voltage and said switch, and having a value selected to sustain the conductive gating condition of said gating circuit for an audibly sensible sustain time interval on opening of said switch.

13. The combination according to claim 12 wherein is further provided a circuit in shunt to said storage capacitor, said circuit including a further diode and a further resistance in series with each other, said further resistance having a value selected to bleed said storage capacitor at a rate selected to sensibly decrease said sustain time interval while said diode is conductive.

14. The combination according to claim 13 wherein is further provided means comprising a voltage source selected to vary the conductivity of said further diode at will, said last means including switch means for at will selectively enabling and disabling said voltage source.

15. In a tone gating circuit for an electronic organ, a continuously operating tone oscillator, a tone bus for collecting said tone, a load coupled to said tone bus, a diode gating circuit connected in series between said tone oscillator and said tone bus and including atleast one diode, key operated means for at will rendering said gating circuit conductive to provide tone signal at said tone bus in response to said tone oscillator said means comprising a source of direct current voltage, a switch connected in a series circuit extending between said source and said diode gating circuit, a relatively large resistance connected in said series circuit and having a value greater than the conductive impedance of said at least one diode when conductive but smaller than the nonconductive impedance of said at least one diode, said direct current voltage having a value and polarity selected to gate on said gating circuit, wherein said tone oscillator, said at least one diode and said load form a series circuit loop, said load including tone color filters and an electroacoustic transducer.

16. The combination according to claim 15 wherein is further provided a storage capacitor connected across said source of direct current voltage and said switch, and having a value selected to sustain the conductive gating condition of said gating circuit for an audibly sensible sustain time interval on opening of said switch.

17. The combination according to claim 16 wherein is further provided a circuit in shunt to said storage capacitor, said circuit including a further diode and a further resistance in series with each other, said further resistance having a value selected to bleed said storage capacitor at a rate selected to sensibly decrease said sustain time interval while said diode is conductive.

18. The combination according to claim 17 wherein is further provided means comprising a voltage source-for varying the conductivity of said further diode at will, said last 7 means including switch means for at will selectively enabling oscillator, diodes and load forming a series circuit including a ground pointlcommon to said oscillator and said load, means for at will rendering said gating circuit conductive, said means comprising a source of direct current voltage, a switch, a high resistance, means connecting said source of direct current voltage, said switch and said high resistance in a series circuit in the order recited between said ground point and the junction of said diodes, said direct current voltage having a value and a polarity selected to render said gate conductiveon closure of said switch, said load including tone color filters and an electroacoustic transducer.

20. The combination according to claim '19 wherein is further provided a storage capacitor connected across said source of direct current voltage and said switch, and having a value selected to sustain the conductive gating condition of said gating circuit for an audibly sensible sustain time interval on openingof said switch.

- 21.1 The combination according. to claim 20 wherein is further provided a circuit in shunt to said storage capacitor, said circuit including a further diode and a further resistance in series with each other, said further resistance having a value selected to bleed said storage capacitor at a rate selected to sensibly decrease said sustain time interval while said diode is conductive.

,22. The combination according to claim 21 wherein is further provided means comprising'a voltage source selected to vary the conductivity of said further diode, said last means virtcludingswitch means for at will selectively enabling and disabling said voltage source.

23. A gating circuit for an electronic organ arranged for at will conveying tone signals froma tone oscillator to a load circuit,comprising'a diode gate circuit connected intermediate said tone oscillator and said'load, said diode gate circuit comprising two diodes connected in series, a source of do. gating voltage, a storage capacitor, a switch, a relatively high'resistance, means responsive to closure of said switch for applying said voltage in parallel to charge said capacitor and via saidjresistance toa point intermediate said two diodes, said resistance having avalue introducing relatively small bypass impedance to said tone signal, and means providing a discharge time constant for said storage capacitor adequate to provide anaudibly'sensible sustain gating voltage to said diode gate on opening of said switch, said load circuit including an electroacoustic transducer. I

'24. The combination according to claim 23 wherein is further provided means including a bias voltage source, means selectively and at will connecting said bias voltagesource across said storage capacitor in the same polarity as said do. gatingvoltage but of substantially small amplitude by a factor of at least 20 percent.

25. A gating circuit for an electronic organ arranged for at will conveying tone signals from a tone oscillator to a load circuit, comprising a diode gate circuit connected intermediate said tone oscillator and said load, said diode gate circuit comprising two diodes connected in series and being normally nonconductive, a source of d.c. gating voltage, a storage capacitor, a switch, a relatively high resistance, means responsive to closure of said switch for applying said voltage in parallel to charge said capacitor and via said resistance to a'point intermediate said two diodes, said resistance having a value introducing relatively small bypass impedance to said tone signal, and a discharge path forsaid storage capacitonsaid discharge path comprising a resistance and a control diode in series and together providing a discharge time constant adequate to provide an audibly sensiblesustain gating voltage to said diode gate on opening of said switch.

26. The combination according to claim 25 wherein is further provided means including a bias volt'age sotirce, means selectively and at will connecting said bias voltage source to bias said control diode in opposition to the bias provided by said source of do gating voltage but of smaller magnitude by a factor of at least percent. v

27. The combination according to claim wherein is further provided means comprising a bias source connected-to said control diode for varying the impedance of said control diode. I

28. The combination according'to claim 27 wherein is provided means form will connecting and disconnecting said bias source to and from said control diode.

29 In an electronic musical instrument having a plurality of continuously operating sources of alternating voltage producing tone signals corresponding to notes of the musical scale, and having an output system for converting electrical signals applied thereto to audible sound, the combination of means comprising a first transmission channel for producing organ tone effect, a means comprising second transmission channel for producing percussive effect, said first and second channels being connected in parallel circuit configuration to said sources, switch means for selectively connecting outputs of said sources to said first channel, circuit means for applying said tone signals to said second channel, said second channel including a plurality of diode percussion gating means having operating and nonoperating states, a common return path between said output system and said sources, means for selectively biasing said gating means from said nonoperating to said operating states, and keyboard means for at will actuating said switch means and said biasing means in pairs, each pair consisting of one biasing means and one switch means connected to a common one of said sources.

30. The combination according to claim 29 wherein each of said gating means includes a first and a second diode, means connecting said first and said second diode in series circuit with said load circuit, means for applying one of said tone signals to said gating means, a further circuit connected between the junction of said first and second diodes and said common return path, said further circuit including resistance means and capacitive means, said means for selectively biasing including a source of direct voltage and switching means, said source of direct voltage having an output voltage at least sufficient to render said diodes conductive, said biasing means selectively connected to charge said capacitive means-to said output voltage in response to actuation of said switch means by said keyboard means, said capacitive means and said resistance means coacting to provide a time constant for providing an audibly percussive rate of discharge of said capacitive means. A Y

31. An electrical musical instrument comprising, an output system having an electroacoustic transducer; generators producing tone signals of different musical frequencies, capacitative-resistive keyer-circuits connecting the generators to said output system for controlling as a function of time the rate of growth and decay of signal voltage supplied the output system in response to activation of said circuits, and nonconductive means selectively insertable in said circuits to prevent decay of signal voltage supplied said output system and cause sustension of sound at said transducer.

32. An electrical musical instrument comprising, an output system having an electroacoustic transducer. generators producing tone signals, resistive-capacitance keyer-circuits connecting the generators to the output system for controlling as a function of time the growth and decay of sound emitted means for selectively connecting said keyer circuits to ground to cause decay of signal voltage delivered to the output system, and electrically nonconductive means selectively connectable in said circuits to block same against decay of signal voltage delivered to the output system and cause sustension of sound at said transducer.

33. An electrical musical instrument comprising, an output system having an electroacoustic transducer, generators producing tone signals of different musical frequencies, capacitive-resistive diode keyer circuits connecting the generators to said output system, said keyer circuits having time constants arranged to control as an audible function of time the rate of growth and decay of signal supplied to said output system in response to activation and deactivation of said keyer circuits in the order named, and means selectively insertable at will in said keyer circuits to decrease only said rate of said decay of said signals to cause a sustain of sound at said transducer.

34. An electrical musical instrument comprising, an output system having an electroacoustic transducer, generators producing tone signals, resistive-capacitance keyer-circuits connecting the generators to the output system for controlling as a function of time the growth and decay of sound emitted by said transducer, each keyer circuit having a control contactor, a common conductor with which the contactors are selectively engageable, a source connected to supply keying potential to said common conductor for activation of said keyer circuits via said c'ontactors, low impedance means for connecting said keyer circuits at will to ground to cause relatively rapid decay of signal voltage delivered to said output system, and high impedance means selectively connectable in said circuits at will to delay said decay of signal voltage delivered to the output system and thereby to cause a sustain effect in the sound provided by said transducer.

35. The combination according to claim 34 wherein said keyer circuits are diode keyer circuits including at least one diode connected between each of said generators and said transducer, each of said keyer circuits further including a storage capacitor in said capacitive-resistive circuits and wherein said high impedance means includes a biased diodei 36. An electrical musical instrument comprising, an output system including an electroacoustic transducer, tone generators, capacitiveresistive diode keyer-circuits connecting the generators to said output system, a source of electrical energy to conduct activating potentialto said keyer-circuits to effect transfer of tone signal between said generators and said transducer, and means selectively coactive at will with all of said keyer-circuits to (l) discharge said keyer circuits rapidly (2) discharge said keyer circuits slowly, said last means comprising double pole sustain switches.

37. in an electronic musical instrument, in combination: a series of signal sources tuned to the notes of the musical scale; each source having a control terminal and being adapted to deliver output signal having an amplitude which is a function of the potential of said terminal; a source of do. activating potential; a playing key operatively connected with each control terminal and with said d.c. source, for changing the potential of said terminal from an original inactive potential to full activating potential; electrical energy storage means connected to each control terminal; and a restoring circuit connected to each control terminal for returning said terminal to inactive potential when potential from said d.c. source is withdrawn; said restoring circuit including a decay circuit connected to each control terminal, which normally returns said terminal to inactive potential in a predetermined period of time; and additional means connected to said decay circuit for speeding up the decay down to a predetermined intermediate potential.

38. In an electronic musical instrument, in combination,

a series of continuously running input signal sources having frequencies appropriate to the notes of the musical scale,

a separate diode gate in series with each of said signal sources,

each of said diode gates having a control terminal and being adapted to deliver output signal from a signal source,

said output signal having an amplitude which is a function of the potential of said terminal,

a source of d.c. activating potential,

playing keys operatively connected with said control terminal and with said do source for selectively changing the potentials of said terminals from an original inactive potential to full activating potential when said keys are selectively, activated,

electronic energy storage means connected to each control terminal, and

a restoring circuit connected to each control terminal for returning said control terminal to inactive potential when potential from said do. source is withdrawn by release of its key, said restoring circuit including a decay circuit connected to each control terminal, which normally returns said control terminal to inactive potential in a predetermined period of time, and Y a shunt to ground for said gate having an impedance selected to bypass said gate to ground only while said gate is nonconductive.

39. The combination according to claim 38 wherein is provided means connected to said decay circuit for speeding up the decay down to a predetermined intermediate potential.

40. The combination according to claim 38 wherein said diode gates each comprises two diodes connected in series and wherein said bypass circuit is connected at least to a point intermediate said diodes, said bypass circuit having an impedance high relative to the conductive impedance of said diodes and low relative to the nonconductive impedance of said diodes.

41. The combination according to claim 38 wherein said diode gates each includes two diodes in series, and means rendering said two diodes alternatively conductive in response to said signal sources.

42. The combination according to claim 38 wherein said switch selectively connects and disconnects one terminal of said electrical energy storage means to ground, said electrical energy storage means including a storage capacitor having two terminals.

43. The combination according to claim 42 wherein is provided a diode connected intermediate said a ground terminal of said capacitor and a contact of said switch.

44. The combination according to claim 38 wherein is provided means connected to said decay circuit for speeding up the decay down to a predetermined intermediate potential, said last means including a diode,

45. The combination according to claim 44 wherein said diode is a diode having a threshold voltage for which conductivity changes radically, said threshold voltage being other than zero.

46. In an electronic organ,

a tone oscillator;

a gate connected in cascade with said tone oscillator;

a load connected in cascade with said gate;

a sustain capacitor;

a timing resistance connected to said sustain capacitor for timing decay of voltage across said capacitor;

key operated means for applying a dc. voltage to said sustain capacitor and thereafter for terminating application of said dc. voltage to said capacitor;

means connecting said capacitor in conductivity control relation to said gate; and

means including a control device for providing a double rate of decay of said voltage across said capacitor operative from the time of said termination of said application of said do voltage.

47. The combination according to claim 46 wherein said double rate of decay includes an initial relatively rapid rate of decay followed by a relatively slow rate of decay.

48. The combination according to claim 47 wherein said control device includes,

a diode; and t v means for biasing said diode to become selectively conductive and nonconductive to establish said initial relatively rapid rate of decay and to establish said relatively slow rate of decay, respectively. I

49. The combination according to claim 48, including a supplemental timing resistance in series with said diode for establishing a supplementary decay path for said capacitor while said diode is conductive which is inoperative while said diode is nonconductive.

50. In an electric musical instrument,

a source of tone signal;

a load; I

said source of tone signal being normally inoperative to provide tone signal to said load; 3 t

key operated means for at will providing application of operating voltage to said source of tone signal to cause said source of tone signal to provide said tone signal to said load;

a normally discharged sustain capacitor so connected to said source of tone signal as to be chargedon said application of said operating voltage;

a double rate decay circuit for the voltage of said capacitor operative following'termination of said application of said voltage; and

said double rate decaycircuit including means forestablishing a relatively rapid decay followed by a relatively slow decay of said voltage of said capacitor and thereby a relatively rapid decay followed by a relatively slow decay of said tone signal in said load. 1

51. The combination according to claim 50 wherein said double rate decay circuit includes a diode and means for biasing said diode to become selectively conductiveand nonconductive to establish said initial relatively rapid rate of decay while conductive and to establish said relatively slow rate of decay whilenonconductive.

52. The combination according to claim 51 including a supplemental timing resistance in series with said diode for establishing a supplementary decay while said diode is conductive which is inoperative while said diode is nonconductive.

53. In an electronic musical instrument, in combination:

a series of signal sources tuned to the notes of the musical path for said capacitor 1 scale;

a control terminal operatively connected with each source;

a source of d.c. activating potential;

a playing key operatively connected with each control terminal and with said d.c. source for changing the potential of said terminal from an original inactive d.c. potential to full activating potential;

electrical energy storage means connected to each control terminal;

a restoring circuit connected to each control terminal for returning said terminal to inactive potential when potential from said do. source is withdrawn;

said restoring circuit-including a decay circuit connected to eachcontrol terminal, which normally returns said terminal to inactive potential in a predetermined period of time; and e additional means connected to said decay circuit for speeding up the decay down to a predetermined intermediate potential.

54. ln an electronic musical instrument, in combination:

a series of signal sources tuned to the notes of the musical scale;

each source having a control terminal and being adapted to deliver output signal having an amplitude which is a function of the potential of said terminal;

a'source of d.c. activating potential;

a playing key operatively connected with each control'terminal and with said do. source, for changing the potential of said terminal from an original inactive potential to full activating potential;

electrical energy storage means connected to each control terminal;

means connected to each control terminal for returning said terminal to-inactive potential when potential from said d.c. source is withdrawn; a

said restoring circuit including a decay circuit connected to each control terminal, which normally returns said terminal to inactive potential in a predetermined period of time; and

, additional means connected to said decay circuit for speeding up the decay down to a predetermined intermediate potential. 

